58 REPORT ON THE TUNICATA OF PLYMOUTH. 



each provided near its extremity with an anterior and posterior 

 longitudinal process ; processes rarely fusing to form complete 

 internal longitudinal bars ; dorsal lamina, a rudimentary or well- 

 developed longitudinal membrane, supporting interserial languettes 

 compressed from side to side. 



Stigmata usually in four, rarely six, transverse rows. 



Stolons delicate, distinct, creeping; branches generally alternate in 

 position. 



The species included within this genus are at present four in number 

 — Listeri (Wiegmann) , Hiitchinsoni (Macdonald),'ym<^ts (Verrill), and 

 banyulensis (Lahille). Of these, P. hanyulensis may prove not to 

 be distinct from P. viridis, as Herdman believes, while P. Hutchin- 

 soni, despite Macdonald's careful description and figures, will pro- 

 bably be found on re-examination to present some structural 

 characters not included in the above generic diagnosis. 



In his recent paper on Ecteinascidia and its allies. Professor 

 Herdman has anticipated me in a description of the interesting con- 

 dition of the interserial papillae in P. viridis. I can quite confirm 

 his account by my observations on a number of specimens of a 

 Perophora which Professor Weldon collected in the Bahamas and 

 gave into my hands some time ago for description. Professor 

 Herdman rightly interprets the bifid or trifid papillae of P. viridis as 

 " rudimentary or imperfect internal longitudinal bars,^' but so far, I 

 believe, no perfect bars have been discerned in the branchial sac of 

 Perophora. In some specimens, however, sent to me from the 

 Zoological Station at Naples, and labelled " Perophora Listeri'' I 

 discovered some months ago that numerous perfect internal longi- 

 tudinal bars actually existed, being supported upon the ends of flat 

 triangular " connecting ducts " precisely as in Rhopalopsis crassa or 

 Ecteinascidia Moorei, with this difference only, that small papillae 

 were frequently present at the points of junction. The existence of 

 papillae on the bars renders the affinity between Perophora and 

 Sluiteria still closer than has been already believed. It is very 

 probable that anew species must be created for the Naples type, but 

 that is a matter to which I hope to refer in a subsequent paper on 

 the anatomy and variation of the genus. (See Postscript, p. 64.) 



3. Peeophoea Listeei, Wiegmann. (PL II, figs. 4, 5, 6.) 



AsciDiA, sp., Lister. Phil. Trans., 18154, pp. 378—382, pi. xi. 



Peeophoea Listeei, Wiegmann. Archives, 1835, p. 309. 



AsciDiA, n. sp., Fleming. Moll. Anim., 1837, pp. 202—209, pi. xvii, fig. 59 (2). 



Peeophoea Listeei, Forbes and Hanley. L. c, p. 28, pi. e, fig. 2. 



— — Giard. Recherches, 1. c, pp. 615, 616, pi. xxi, figs. 3, 6 



to 11, 13 to 15, pi. xxiv. 



